Method and apparatus for filament spinning



Jan. 5, 1960 c; E. HIESERMAN' ETAL METHOD AND APPARATUS FOR FILAMENTSPINNING Filed Nov. 14, 1957 INVENTORS CLARENCE E. H/ESERMAN C24RRE TTLEW/ BY ATTORNE VS Unite rates Patent Office 2,919,465 Patented Jan. 5,1960 minor) AND APPARATUS FOR FILAMENT SPINNING Clarence Hieserman andLewis C. Garrett, Decatur, Ala., assignors to The ChemstrandCorporation, De-

catur, Ala., a corporation of Delaware Application November 14, 1957,Serial No. 696,37? '4 Claims. (31. 18-8 This invention relates to amethod and apparatus for filament spinning and more particularly to amethod and apparatus for circulating the coagulating liquid in a spinbath employed in the wet-spinning of continuous filaments of a syntheticmaterial such as that formed from acrylonitrilc polymers and the like.

In one type of spinning operation known generally as Wet spinning forproducing synthetic filaments, a spinning material or dope is suppliedto a spinning device or 'spinnere'tte, the face of which is providedwith a plurality of spinning orifices. During spinning, the spinneretteis immersed in a coagulating liquid or bath so thatthe spinning materialextruded from the orifices reacts with the liquid and solidifies to forma bundle of continuous filaments. The orifices in the spinnerette facemay be of any desired number, spacing and diameter in accordance withthe filamentary end product to be produced, v

As is well kown,in such spinning operations the hot spinning material(generally 75 to 90 C.) adds considerable heat to the relatively coolspin bath.

Furthermore, during the process of filament coagulation, not only isbath concentrating liquid transferred from the filaments to the bathduring coagulation, but reaction products from the coagulation processare added to'the liquid which are contaminating in nature. In such spinbath arrangements, therefore, a circulation of the bath is highlydesirable to maintain the normally critical bath teniperature at itspredetermined level and to present relatively uncontaminated anduniformly concentrated coagulating liquid to the spinning material andto the coagulated filaments prior to emergence from the bath. Thiscirculation becomes increasingly important adjacent the face of thespinnerette in the zone where the spinning material initially solidifiesto form the individual filamerits.

Ina spinning operation where the number of filaments arerelatively largein number, in size, or both, or Where the orifices are closely spaced,the denseness or compactness of the bundle or end of filaments obstructsor reduces the circulation of the coagulating liquid in the baththroughout the face of the spinnerette as well as the central "area ofthe filament bundle. In addition, the location of the spinnerette insome spinning arrangements produces *an interruption of the flow patternthroughout the spin 'bath and gives a relatively static conditionadjacent the faceo'fthe spinneret'te.

It has been found that when improper heat transfer conditionsexist atthe spinnerette face and the bath temperature is not maintained constantas a result of poor bath circulation, filaments of erratic andnon-uniform properties are formed. This irregular filament formation:presents a serious problem during the subsequent filament washingoperation and renders the complete removal of solverit from thefilaments difiicult, if not impossible, Furthermore, non-uniformfilaments mean that thephysical characteristics of the yarn and fabricformed ffoin these filaments do not measure up 'to specific 'reiiifr'fnefifs. In addition t'othe lack of bath temperature control,further difficulty is experienced in filament quality control as theconcentration of the bath varies where it contacts the filaments and asa result of the presence of excessive contaminating material in the bathwhich has not been removed. It has been proposed to increase thecirculation of the bath liquid to maintain bath uniformity. However,this approach has resulted in the creation of turbulence in the bathwhich produces a deleterious effect during filament formation andcoagulation.

Accordingly, a primary object of this invention is to provide a new andnovel filament spinning method and apparatus.

Another object of this invention is to provide a new and improvedwet-spinning apparatus for spinning continuous synthetic filaments whichprovides a highly efficient circulation of coagulating liquid throughoutthe spin bath.

A further object of this invention is to provide a new and novelarrangement for a wet-spinning operation which enables the presentationof coagulating liquid at the proper concentration and temperature to thespinning material emerging from the orifices of a spinnerette at alltimes throughout the spinning operation.

Still another object of this invention is to provide a new and improvedfilament spinning apparatus which enables the spinning of continuousfilaments of synthetic material formed from acrylonitrile polymers andthe like from which the coagulating liquid may be easily removed in athorough manner during a subsequent Washing operation and which producesfilaments having physical characteristics which are substantiallyuniform throughout.

This invention further contemplates the provision of a new and improvedfilament spinning apparatus which includes an arrangement forcirculating the spin bath coagulating liquid in a positive andpredetermined manner Without the need for a high rate of circulationwithin the bath tank and which insures that all portions of the formedfilaments, particularly those portions directly adjacent the spinningorifices, are reacted with properly concentrated, coagulating liquidwhich is substantially free of contaminating decomposition products, andwhich is maintained with a high degree of accuracy at a predeterminedtemperature level.

Other objects and advantages of the invention will become apparent fromthe following description taken in in connection with the accompanyingdrawings.

The specific objects of the invention are accomplished by providing acontainer or tank for a spin bath in which is positioned in anyconventional manner a spinnerette having a plurality of orifices withinits face. The container is filled to theproper level with coagulatingliquid so that the spinnerette is immersed therein and spinning materialextruded through the spinnerette orifices is coagulated into filamentaryform upon contact with the liquid. Nozzle means are positioned adjacentthe face of the spinnerette and are arranged to inject a secondary flowof coagulating liquid outwardly from the face of the spinnerette toinduce a liquid fiow or current throughout the space or-zone defined bythe spinnerette face and the nozzle means and to circulate bath liquidwithin the central area of the spun filament bundle.

The novel features which are believed to be characteristic of theinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its organization and method ofoperation, maybe bestunder'stood by reference to the followingdescription taken in conjunction with the accompanying drawing in which:

Figure 1 is 'a'side view showingfilament spinning app'ar'atusconstructedin accordancewith the invention;

Figure 2 is an enlarged perspective view of a portion of the apparatusof Figure 1 illustrating the invention; and

Figure 3 is an enlarged view taken substantially along line 33 of Figure1.

As generally illustrative of the invention there is shown in Figure l atank or container 11 in which is suspended in any suitable manner aspinnerette 12 of the type for extruding or ejecting a syntheticfilamentary material or dope such as material formed of acrylonitrilepolymers or the like. The spinning material is supplied to thespinnerette 12 by a conduit or supply line 13 suitably connected to thespinnerette as shown and which is connected at its other end to asuitable source of spinning material designated generally by the numeral14. As shown, the conduit 13 may be pivoted at 16 so as to permit thespinnerette 12 to be moved from an elevated position above the tank 11to the supported spinning position shown in Figure 1 wherein thespinnerette is rigidly held in a generally inclined plane in the wellknown manner.

The tank 11 is filled with a coagulating liquid 17 which is continuouslysupplied to the tank 11 by means such as an inlet18 so that thespinnerette 12 is immersed in the coagulating liquid 17 during thespinning operation. The liquid level in the tank may be maintained bymeans of an outlet 19 through which liquid moving across the tank flowscontinuously.

As is well known, spinning material or dope preferably in a viscousfluid form is fed to the spinnerette 12 through the conduit 13 anddischarged through a plurality of orifices 21 in the spinnerette face 22(Figure 2). As is well known, the viscous dope emerging from the orifices 21 solidifies upon contact with the coagulating liquid 17 andforms a plurality of filaments 23 which are subsequently directed aroundsnubber bars 24 and removed from the tank 11 in the form of afilamentary tow 26.

In spinning operations where the spinnerette face 22 contains a highnumber of orifices relative to the area of the face or where theorifices are relatively closely spaced, a dense or compact bundle offilaments is formed so that it is relatively difficult to obtainadequate circulation of the spinning solution 17 throughout each of thefilaments 23 in the tow 26. This circulation problem is considerablymagnified in the portion of the bundle of filaments directly adjacentthe spinnerette face 22. It has been found in such spinning arrangementsthat the circulation of the liquid bath 17 is greatly reduced adjacentthe spinnerette face 22 not only as a result of the denseness of thefilamentary bundle, but additionally by the liquid currents set up bythe moving filaments 23. It has been found that the moving filamentsactually set up current spaced aroundtne bundle which move in theopposite direction from the filaments and which tend to create asomewhat static condition at the spinnerette face. Furthermore, inspinning apparatus as shown in Figure l, the position of the spinnerettetends to obstruct the flow of liquid in its laminar flow across the tank11 from the inlet 18 to the outlet 19.

As is understood, the filaments 23 are initially formed as the dopeemerges from the spinnerettes orifices 21 and the physical and chemicalstate of the coagulating liquid 17 is, therefore, very critical at thispoint. It is well known that the temperature of the coagulating liquid17 is very critical in the proper formation of filaments 23 particularlyin the spinning of filaments formed from acrylonitrile polymers and thelike. The relatively hot dope emerging from the orifices 21 transfersrelatively large quantities of heat to the bath as a result of therelatively low temperature liquid in the bath. Unless the liquid isconstantly replaced with fresh solution at this point in particular thisheat is not removed, and the bath temperature at the spinnerette facerises appreciably causing severe limitations in the filament formingoperation such as inadequate solvent removal in subsequent washing stepsand highly erratic and non-uniform physical properties in the spunfilaments. Furthermore, poor circulation of the bath at the spinnerettecauses a material change in the concentration of the bath furthercontributing materially to the improper formation of the filaments. Asis Well known, the filament coagulating process is one of solventremoval. Improper bath circulation, therefore, not only produces poorresults adjacent the spinnerette face, but as the bundle of formedfilaments move within the bath, the coagulating liquid throughout thecentral portion of the filament bundle increases in concentration withthe continuous transfer of solvent to the bath from the filaments. Thus,for proper results, bath circulation must be effectively carried outadjacent all portions of the filaments immersed in the bath 17. Previousattempts to increase bath circulation by high bath liquid feed rates orby moving bath liquid across the tank in a direction opposite to thedirection of filament movement only created turbulence in the filamentbundle which produced improper filament formation.

Means, therefore, have been provided to increase the circulation of thecoagulating liquid 17 adjacent the face 22 of the spinnerette 12 andaccurately control the formation of the filaments 23. More specifically,there is provided nozzle means as shown in Figures 2, 3 designatedgenerally by the numeral 27 for injecting a secondary flow ofcoagulating liquid into the tank 17 and for inducing a radially inwardliquid flow across the face 22 of the spinnerette 12 and within the areadefined by the spinnerette face and the nozzle means. In the specificembodiment shown, the nozzle means 27 comprises a tubular ring 28 whichis positioned forward of the spinnerette face 22 as shown in Figure 2and preferably within a plane substantially parallel to the spinneretteface.

The ring 28 may be supported in any suitable manner. For instance, thering 28 may be supported on the spinnerette 12 by means such as abracket 29 suitably secured at opposite ends to the spinnerette 12 andring 28 as shown best in Figure 2.

The ring 28 contains a central opening 31 which encompasses or encirclesthe bundle of filaments 23 moving outwardly from the spinnerette face 22and toward the snubber bar 24. On the side of the ring 28 opposite fromthat of the spinnerette 12, port means are provided for injecting asecondary flow of liquid preferably coagulating liquid as in thecontainer 11 outwardly from the spinnerette face 22. In the specificembodiment illustrated the port means comprise a plurality ofcircumferentially spaced openings or ports 32 which preferably extendcompletely around the side of the ring opposite from that of thespinnerette 12.

In order to supply liquid to the interior of the ring 28, a conduit 30is connected to the ring in any suitable manner as shown in Figure 3.The conduit 30 is connected at its other end to a suitable source ofliquid so that liquid may be fed continuously to the interior of ring 28and discharged outwardly through the ports 32 in a plurality ofsecondary streams 33. Although the streams 33 may be directed in anygenerally outward direction from the spinnerette face 22, the ports 32are so located that the streams flow in a slightly converging manner asshown in Figure 2. However, if desired, any flow direction may beselected in accordance with the desired flow pattern such as in adirection substantially perpendicular to the spinnerette face 22.

During the spinning operation, the coagulating liquid 17 is suppliedcontinuously with fresh liquid from the inlet 18 and flows outwardlythrough outlet 19 as previously described. Spinning material is suppliedto the conduit 13 and thence through spinnerette 12 to form filaments 23which pass coaxially through the opening 31 in the ring 28 as shown, andwhich are directed subsequently over snubber bars 24 in the form of tow26. In accordance with the invention, coagulating liquid is suppliedthrough conduit 30 to the ring 28 and a plurality of liquid stream:

33 emerge from ports 32 outwardly from the face of the spinnerette 12.

In the space or zone defined by the spinnerette face 22 and the ring 23a secondary flow of coagulating liquid 17 is induced by the reaction tothe secondary streams 33 and the liquid flows across and throughout thespace as indicated by the multiple arrows H in Figure 2. Thus freshcoagulating liquid which is properly concentrated, uncontaminated, andof the proper temperature is continuously supplied to the spinningmaterial emerging from the orifices 21 and filaments 23 of the properphysical and chemical characteristics are formed. With this arrangementthe denseness or compactness of a filamentary bundle does little toinhibit circulation of the coagulating liquid. As the secondary streams33 are directed so as to converge slightly the streams will move intothe bundle of filaments 23 to prevent the build-up of highlycontaminated bath liquid within the central portion of the bundle.

It has been found in practice that this induced flow of bath liquidadjacent the spinnerette face 22 is best obtained when the ring 28 islocated at a distance between /2 to 2 /2 inches forwardly of thespinnerette face 22. For example, satisfactory performance has beenobtained When the ring 28 is located approximately 2 inches forwardly ofthe spinnerette face 22.

It can be seen that there has been provided a novel arrangement forpresenting coagulating liquid or solution to spinning material emergingfrom a spinnerette in a filament spin bath in which the bath isconstantly maintained at the proper temperature and concentration toenable a uniform filamentary tow to be produced having the desiredphysical and chemical properties. Circulation of the bath isaccomplished in a simple and easy manner and the flow of coagulatingliquid through the main bath may be maintained at a relatively low levelto avoid any turbulence within the filaments. Furthermore, it can beseen that the induced current flow produced by the invention is capableof wide variation which may be brought about by changing theconfiguration of the ring 28 and the size, shape, and position of theports 32 within the ring. For instance, both the direction and thequantity of secondary flow may be varied to induce current flow ofgreater variety.

While there has been described what at present has been considered to bethe preferred embodiment of the invention, it will be understood bythose skilled in the art that various changes and modifications may bemade therein without departing from the invention and therefore it isthe aim of the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

Having thus described the invention, what is claimed is:

1. Apparatus for wet spinning synthetic filaments comprising, incombination, a container for filament coagulating liquid, inlet meansfor supplying fresh coagulating liquid to said container, outlet meansfor removing coagulating liquid from said container, a spinnerettesupported in said container for immersion in said filament coagulatingliquid, a tubular ring positioned concentrically with said spinnerettein close encompassing relationship with the bundle of filaments normallyadvancing from said spinnerette, and port means in said ring adapted toinject a secondary flow of fresh coagulating liquid into said filamentcoagulating liquid in said container in a generally outward directionfrom the face of said spinnerette, said ring being entirely spacedforward with respect to the face of said spinnerette so as to define anannular zone therebetween and concentric therewith, whereby a radiallyinward current flow of coagulating liquid in said container into saidannular Zone will be induced when the coagulating liquid issues fromsaid port means.

2. Filament spinning apparatus in accordance with claim 1 wherein saidtubular ring is provided with a plurality of circumferentially spacedopenings in the side of said ring opposite said spinnerette face, saidopenings in said tubular ring being arranged to emit a plurality ofstreams outwardly from the face of said spinnerette in a convergingrelationship.

3. In the manufacture of synthetic filaments by the wet spinning processwherein a coagulable spinning material is extruded through the orificesof a spinnerette immersed in a filament coagulating liquid in acontainer therefor to form a bundle of densely packed syntheticfilaments, said filament bundle being continuously withdrawn from saidfilament bath, and wherein the filament coagulating liquid iscontinuously flowed radially toward the extrusion axis in a zone normalto and adjacent the spinnerette, the improvement comprising the step ofestablishing a radially inward current flow of filament coagulatingliquid into said zone and into said filament bundle by introducing intosaid filament coagulating liquid at a point entirely and slightlyforward with respect to the face of said spinnerette a plurality ofstreams of fresh coagulating liquid arranged in an annular pattern andclosely encompassing said filament bundle, the direction of said streamsbeing generally outward from the face of said spinnerette.

4. The method as defined in claim 3 wherein the directional flow of thestreams of fresh coagulating liquid is in a converging direction.

References Cited in the file of this patent UNITED STATES PATENTS2,642,333 Tomonari et a1. June 16, 1953 FOREIGN PATENTS 501,476 BelgiumMar. 15, 1951

